Gnomonia leaf blotch, caused by the fungal pathogen Gnomonia comari, is a disease affecting strawberry plants in the Southeast. This pathogen primarily targets the foliage; however, it has the potential to infect flowers and fruit. In some instances, the leaf blotches can cause defoliation, which can in turn affect fruit yield and quality. Understanding the symptoms, disease cycle, and effective management strategies is essential for maintaining healthy strawberry crops and developing an integrated pest management (IPM) strategy for season-long control.

Gnomonia Leaf Blotch

Symptoms

The initial and most prominent symptom is the appearance of target shaped, brown to dark purple spots on the strawberry leaves. As the disease progresses, these spots may merge, forming larger blotches that can cover significant portions of the leaf surface. In severe infections, the affected areas may become necrotic, causing the leaves to wither and die. Severe cases of Gnomonia leaf blotch can lead to a noticeable reduction in fruit size and quality. In rare instances, Gnomonia has been known to cause blotches on fruit. Gnomonia is most often associated with the source of plant material. This pathogen often arrives on plugs but can also survive on plant material left in the field from the previous season.

Management Strategies

Crop rotation is crucial for reducing disease pressure in strawberry production. This practice will also reduce the incidence of more serious pathogens, such as phytophthora, anthracnose, and nematodes. Growers should also regularly remove and destroy infected leaves and plant debris to reduce the inoculum load in the field.

The application of fungicides during the early stages of leaf development is crucial, especially during periods of wet weather. Products containing captan, myclobutanil, or thiophanate-methyl have shown effectiveness in controlling Gnomonia leaf blotch as well as other leaf spot diseases.

More Information

Effective management of Gnomonia leaf blotch in strawberries requires a combination of cultural practices and chemical control. While this disease rarely has any severe economic impact, it is important to maintain healthy plants to reduce stress which may allow other pathogens to persist. Regular monitoring, early detection, and timely application of fungicides, along with maintaining good field hygiene and crop rotation, are important in preventing damage and ensuring quality fruit production.